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Tuesday over running event


Mitchel Volk

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Just not sure with minus 5 with .5 falling the BL doesn't cool. ( as long as the 925 sr ok)

That was 850 to 700mb critical thicknesses. It's Showing an EWL somewhere in there most likely due to the strong flow into the significant mid level Ridge. However there also may be the potential there for some decent frontogenesis. Potential is certainly there for an elevated warm front as the incoming warmer air rides over the cold pool. This is reflected nicely on 700mb. I haven't looked at frontogenesis maps for the nam or 4k nam but suspect it would show this nicely.

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I've always assumed the fetch of moist air coming in with a storm off the coast includes air originating hundreds of miles away, like off the Gulf Stream, which is much warmer than the mid-30s. Not sure what the aggregate air temp coming in via SE winds is, but I imagine it's warmer than just the air right off the coast.

Your assumption is correct. All those mid 30 temps near the coast can't do much when the fetch stretches much further than that.

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I've always assumed the fetch of moist air coming in with a storm off the coast includes air originating hundreds of miles away, like off the Gulf Stream, which is much warmer than the mid-30s. Not sure what the aggregate air temp coming in via SE winds is, but I imagine it's warmer than just the air right off the coast.[

 

SSTs in 40s about 25 to 50 miles offshore:

 

2014021700_highResSst_NEC.png

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SSTs off the coast are in the lower to mid 30's, SE wind isnt going to hurt like in Dec

I think it depends on where you are. If you are on the immediate coast by about 5-8 miles a low level SE wind at 15-30knts, even with 850s at -5, can still end as liquid at the surface. I am right near the coast and spiked to 42 degrees yesterday before the precip really picked up and winds came out of the NE.

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We had snow here a few weeks ago with strong SE winds and a surface temp of around 25. Deference then and now is we had a very cold antecedent air mass to our south. The air mass we have now is much warmer than that plus we have no real HP to north, only the existing one that moves into an unfavorable spot east of Newfoundland.

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Not so straight forward, if the secondary develops a little faster then the se winds will be weaker and then shift quicker to a more easterly position then the BL holds off the warmer a little longer. Another important thing to watch is the trajectory of the wind at this point it is not very good. Another factor will there be a little cold air damming, if so then the snow would last longer. These are some of the issues to look at. It is not the easiest forecast to make. The exact time of the changer over can be from 12Zto 15Z for Central Park. Every minute will make a big difference of accumulations. Areas at the immediate coast the accumulations will be minimal . While HPN will see mainly snow.

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Not so straight forward, if the secondary develops a little faster then the se winds will be weaker and then shift quicker to a more easterly position then the BL holds off the warmer a little longer. Another important thing to watch is the trajectory of the wind at this point it is not very good. Another factor will there be a little cold air damming, if so then the snow would last longer. These are some of the issues to look at. It is not the easiest forecast to make. The exact time of the changer over can be from 12Zto 15Z for Central Park. Every minute will make a big difference of accumulations. Areas at the immediate coast the accumulations will be minimal . While HPN will see mainly snow.

True, Feb 22 2008 might be a decent analog here, although that had the secondary further south and dumped 4-8" area wide ending in drizzle.

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True, Feb 22 2008 might be a decent analog here, although that had the secondary further south and dumped 4-8" area wide ending in drizzle.

 

3/9/82 is now the best analog appearing on CIPS...the setup is not as good as this one as the initial low went more inland and no coastal formed...but LGA did see snow for a few hours before the BL torched but as you can see in the obs even with a southerly of 15 knots it took hours to get substantial warmth and that was with very little snow falling, more sustained snow would likely have allowed temps to stay cooler.

 

http://www.meteo.psu.edu/~fxg1/NARR/1982/us0309.php

 

http://www.wunderground.com/history/airport/KLGA/1982/3/9/DailyHistory.html?req_city=La+Guardia&req_state=NY&req_statename=New+York

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Meh, I'm regardless expecting an inch or two here and within 15 miles or so of the coast despite any redevelopment. If it's really weak we see the inch or two and then precip ends as drizzle, if stronger the inch or two and then soaking rain. Of course inland has more riding on it. Best of luck Manhattan/Bronx on NW.

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ARW

i5vda9.gif

 

NMM

qq4o7m.gif

 

Both impressive

Very likely not for you and I unless winds can pivot away from SE. Unless that happens we have a very low ceiling for how much snow we can get before rain. Maybe very heavy rates can hold that off, but SE winds are very dangerous to play around with any time of the year. It had hopefully be in the low-mid 20s at highest when the snow moves in to give some breathing room. The ocean is pretty cold as well but the SE fetch is pretty far and can still overwhelm with warm enough boundary layer air for near the shore.

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Very likely not for you and I unless winds can pivot away from SE. Unless that happens we have a very low ceiling for how much snow we can get before rain. Maybe very heavy rates can hold that off, but SE winds are very dangerous to play around with any time of the year. It had hopefully be in the low-mid 20s at highest when the snow moves in to give some breathing room. The ocean is pretty cold as well but the SE fetch is pretty far and can still overwhelm with warm enough boundary layer air for near the shore.

If the SE winds are not strong, we will be fine.  We also need good rates. I like the look of the mesoscale models ( NMM and ARW )

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This is morphing from an overrunning event into a combo that could include precipitation from a coastal. Both hi-res models are impressive and their solutions aren't terribly different from the NAM and EURO -- temp profiles on the ARW/NMM are favorable for the duration of the event, as well.

 

It seems that they may be picking up on yet another last-minute trend. This is something to watch, and while 2-4" for the metro looks likely, a narrow swath of 6"+ totals is within the realm of possibilities; it would come in an extreme thump late Tuesday AM.

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Me thinks we see a cave to higher QPF.  Last minute trend here it looks like. .5" contour back to Eastern NJ and east.

Indeed. 06z NAM is 4-6" for NYC. Impressive increase in QPF. If the hi-res models are any indicator, we will see additional increases; could parts of the region see another event of 10"+? We shall see...

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